Typically, reliable communications facilitate the effective operation of some systems. For example, radio communication between an aircraft and a base on the ground facilitate for safe operation of the aircraft and mission success.
Many aircraft utilise a number of communication and data link systems to enable them to carry out their missions. Typically, these systems are connected to one or more dedicated antennas. The proximity of these antennas to each other, especially on an aircraft with space restrictions, can create a phenomenon known as “co-site” interference.
Serious problems can occur when a transmitter antenna is located within the vicinity of a receiver antenna. In particular, weak or distant signals that a receiver is normally capable of receiving may be lost in the low-level broadband noise created by a co-site transmitter. This effect is referred to as “receiver de-sensitisation”.
One solution to the problem of receiver desensitisation is to increase antenna RF isolation by increasing the spatial separation of receiving and transmitting antennas. However, this is not always possible on platforms which are of limited size.
Another solution to the problem of receiver desensitisation is to use an RF filter for both the transmitters and receivers. Receivers are filtered so that they only receive a specified bandwidth at the chosen frequency, while transmitters are filtered to reduce broadband noise and sidebands. However, the filters used in this configuration tend to be large, heavy, expensive, and consume relatively large amounts of aircraft power. Furthermore, the filter installations tend to be bespoke and have to be adapted to the particular type of aircraft. Also, the filters themselves generally require software and hardware integration with the donor radio system allowing access to the radio tuning bus and discrete signals. Thus, the filter installations cannot be transferred to other radio systems in the event of a platform radio upgrade, equipment obsolescence update etc.